Process for the preparation of fibre suspensions



. Feb. 5, 1963 K. ROSENFELD ETAL 3,076,610

PROCESS FOR THE PREPARATION OF FIBRE SUSPENSIONS Filed July 10, 1961 2Sheets-Sheet l no r- :1 N a, m N N cn o 9 S 9- on 1- --w U'l a (-1 (O BElm Feb. 5, 1963 K. ROSENFELD ETAL 3,076,610

PROCESS FOR THE PREPARATION OF FIBRE SUSPENSIONS Filed July 10, 1961 2Sheets-Sheet 2 United States Patent 3,076,610 PROCESS FOR THEPREPARATION OF FIBRE SUSPENSIONS Klaus Rosenfeld, Weissenau, and GiiuterMickley, Ravensburg, Germany, assignors to Escher Wyss G.m.b.H.,Ravensburg, Wurttemberg, Germany, a corporation of Germany Filed July10, 1961, Ser. No. 122,923 Claims priority, application Germany July 14,1960 7 Claims. (Cl. 241-28) This invention relates to a process for thepreparation of fibre suspensions, more particularly in paper making, aswell as to an application of this process and an installation forcarrying out this process.

So-called dispersing devices are known, in which a hub disc with annularrows of teeth arranged coaxially on it relatively rotates with respectto a second disc with annular rows of teeth arranged coaxially on it,the said rows of teeth of one disc projecting into gaps left between theannular rowsof the other disc, and "the material to be treated flowsbetween the two discs alternately through the teeth rows of the twodiscs from a central orifice of one of the discs from the insideoutwardly. These known dispersing devices operate with pulpconsistencies (i.e., the ratio of the weight of dry solids in the pulpto the total weight of the wet pulp expressed as a percentage) of 7 to8%, and serve merely. for removing specks from the material withoutmechanically working the individual fibres.

In the preparation of waste paper, for example, it is necessary toseparate or disperse the printers ink carried by the paper, as well asportions of dirt and wax, which adhere to the material broken up in awet mixer.

The ink particles, for example, can be removed chemically by solution orflotation. It is also known to comminute and disperse the ink particlesin the fibre material mechanically by treating the material in anedgerunner mill so finely that they are no longer perceptible to theeye.

Furthermore, a known process operates with a so-called one-shaft pulperat high pulp consistencies and at temperatures up to 95 C. For attainingthese pulp consistencies extensive separate thickening apparatus isrequired, the high temperatures being obtained by the addition of steam.

It is now the object of the invention to simplify and improvesubstantially the preparation of fibre suspensions compared with theknown processes. In a process of the kind hereinbefore described, forthis purpose, according to the invention, the fibre suspension isconcentrated to a fibre pulp of at least 15% consistency, and this pulpis conveyed to a dispersing device known per se, which (as describedhereinbefore) comprises relatively rotating coaxially arrangedinterengaging annular rows of teeth, the said concentrated pulp beingled through the interstices of said teeth in a substantiallyradialdirection.

The invention is based on the discovery that the apparatus usedheretofore only for low pulp consistencies and only as a speck removeris an extremely efiective preparation apparatus, requiring little power,for the individual fibres and fibre agglomerates, and also represents anequally eifective dispersing apparatus for the ink particles and thelike contained in the material to be prepared, if the fibre suspensionto be prepared is brought to a pulp consistency of at least 15 for theduration of stay in the apparatus.

In fact, in this condition of the material, the individual fibres areprocessed in the dispersing device, without being shortened or damagedmechanically in structure, by friction effects from fibre to fibre, sothat they become completely pliant and flexible. Due to these newproper- 3,076,610 Patented Feb. 5, 1963 ties, in the subsequentformation of the paper sheet, the fibres can be laid closer together andfelted better, resulting in considerably greater strengths in the driedpaper sheet. Heretofore, an increase in the paper strength has only beenpossible by so-called grinding in different grinding machines, in which,however, the individual fibres are shortened mechanically and damaged intheir structure, the facility of removing water from the fibre fleecebeing thereby considerably reduced.

In addition to the improvement in the individual fibres, with a pulpconsistency of at least 15% in the dispersing device, there is alsoobtained, likewise by friction effect, a temperature adequate forsatisfactory dispersion, without the necessity for an external supply ofheat. In addition, it is not only possible to disperse the printing inkand wax particles satisfactorily in the preparation of waste paper, butthe chemical accessory agents and additives, for example, dyes, waxes,starch, resins and so forth can be added to the paper pulp for obtainingcertain properties in the finished paper. The accessory agents andadditives are advantageously added to the paper pulp after concentrationto a pulp consistency of at least 15 The thorough mixing and dispersingof the chemical accessories and additives is so good in the processaccording to the invention that the chemicals are dispersed practicallyuniformly on or worked into the surfaces of the individual fibres.Compared with the usual processes, this results in a considerable savingof accessory substances, as Well as substantial improvements inproperties of the paper which are aimed at by the additions.

The best results can be obtained if, before introduction into thedispersing device, the fibre suspension is concentrated to a fibre pulpof 20 to 25% pulp consistency. The liquid removed from the fibresuspension during concentration can be returned at least partly to theconcentrated fibre pulp after the latter has been treated in thedispersing device. This liquid, or another liquid, or both, can be usedfor washing the fibre pulp out of the outlet housing of the dispersingdevice and for re-diluting the fibre pulp to a fibre suspension which issuitable for further processing and which can be pumped. vTheapplication of the process according to the invention is particularlyadvantageous for the preparation of waste paper in dispersing printingink, wax particles and the like, with simultaneous disintegrating of thefibre bundles and specks into individual fibres.

An installation for carrying out the process according to the inventionis represented in simplified manner in the drawing by way of example.

FIG. 1 shows an axial vertical section through the installation,

FIG. 2 shows a portion of FIG. 1 on a larger scale, and

FIG. 3 shows a section on the line III-III of FIG. 2.

The installation shown has a dispersing device 1, driven by a motor 2 bymeans of a shaft 3 journalled in bearings 4 and 5. Mounted on the shaft3 is a hub disc 6,

which carries annular rows of teeth 7 arranged coaxially to the shaft 3and rotates in a housing 8. On one wall of the housing, there is fixed,parallel to the hub disc 6, a stationary disc 9 carrying concentric rowsof teeth 10. The housing 8 has an inlet orifice 11 and a radial outlet12 of large cross-section. The dispersing device 1 is preceded directlyby a thickening worm press 13. A motor 14 drives an agitator arm 17arranged in the inlet 16 of the worm press 13 and, by means of gearing15, a worm 18 which rotates in a perforated casing 19. The end 20 of thecasing 19 joins directly on the inlet orifice 11 of the dispersingdevice 1. An outer shell 21 of the worm press 13 defines a water chamberhaving a liquid outlet 22, while the outlet part of the housing 8 of thedispersing device 1 is provided with a liquid inlet 23.

From the liquid outlet 22, a pipeline 24, including a pump 25, leads tothe liquid inlet 23.

The material to be prepared, broken up in a wet mixer of known kind issupplied at a still pumpable pulp denvSity of to 6% to the inlet 16 ofthe worm press 13, and in the latter, is freed from a part of itsliquid. 'The liquid collects in the outer shell 21 and flows awaythrough the connection 22. The material, thickened in the worm press to2G to 25% pulp consistency is prepared in the dispersing device 1, inwhich it flows in a substantially radial direction alternately throughthe interstices of the rotating and stationary teeth rows. After thematerial passes through the interstices of the rows of teeth, it entersthe diffuser or outlet section of the disperser where it is againdiluted. For this purpose, dilution liquid is supplied to the diffusersection through inlet 23. In addition to diluting the material beingprocessed, this dilution liquid also serves to wash the material out ofthe diffuser section. The diluted material is discharged from thedisperser through the outlet 12 leading from the diffuser section.

The combination of the dispersing device and the worm press, arrangedcoaxially with it to form a machine unit, gives a particularly compact,efiicient installation. The concentration of the material to theconsiderable pulp consistency of 20 to 25%, at which it can no longer bepumped, is limited in practice to the short processing period in thedispersing device itself. At the same time, the worm press is a muchsimpler and more economical concentrating apparatus than the thickeningapparatus of the known processes.

The concentration of the material to be prepared may, however, also becarried out in some other way, in which case it is necessary to have aspecial conveying device for conveying the thickened, no longer pumpablematerial into the grinding and dispersing apparatus.

Such a special conveying device may be dispensed with if the shaft ofthe dispersing device is arranged vertical. In the vertical position ofthe device which is shown in the drawing, the pump 25 in the liquidpipeline 24 is also not required.

What is claimed is:

1. Process for the preparation of a fibre suspension, more particularlyin paper making, which consists in concentrating the said fibresuspension by removal of liquid to a fibre pulp of at least pulpconsistency and treating the so-obtained fibre pulp by leading it in asubstantially radial direction through the interstices of relativelyrotating coaxially arranged interengaging annular rows of teeth.

2. The process defined in claim 1 in which the concentration of thefibre suspension is effected to a pulp consistency of between 20% and25% of the fibre pulp.

3. The process defined in claim 1 in which the liquid removed during theconcentration of the fibre suspension is returned at least partly to theconcentrated fibre pulp which has been led through the interstices ofthe said interengaging annular rows of teeth.

4. The process defined in claim 1 in which chemical accessories andadditives, for obtaining predetermined properties of the finished paper,are added to the fibre suspension after its concentration.

5. The process defined in claim 1 as applied for the preparation ofwaste paper in dispersing printing ink, wax particles and the like withsimultaneous disintegration of the fibre bundles and specks into theindividual fibres.

6. An apparatus for treating fibre suspensions comprising a dispersingdevice having a hub disc with annular rows of teeth arranged coaxiallyon it and a second disc with annular rows of teeth arranged coaxially onit, the teeth rows of one disc projecting into gaps left between theteeth rows of the other disc and the said discs being mounted so as toallow relative rotation with respect to one another and one of saiddiscs having a central opening for the concentrated fibre pulp to betreated; and a housing defining an outlet space for the treated pulp;and a worm press including a dewatering chamber and having an inlet forthe fibre suspension to be concentrated and an outlet for theconcentrated fi-bre pulp; said worm press being arranged coaxially withsaid dispersing device and being directly connected to the dispersingdevice in such a manner that the outlet of the worm press opens into theinlet of the dispersing device.

7. The combination defined in claim 6 comprising a pipeline leadingdirectly from the dewatering chamber of the worm press to the outletspace of the dispersing device housing.

References Cited in the file of this patent UNITED STATES PATENTS1,493,535 Haug May 13, 1924 2,645,464 Forbes July 14, 1953 2,761,799Schroeder Sept. 4, 1956 FOREIGN PATENTS 40,371 Sweden Mar. 15, 1916

1. PROCESS FOR THE PREPARATION OF A FIBRE SUSPENSION, MORE PARTICULARLYIN PAPER MAKING, WHICH CONSISTS IN CONCENTRATING THE SAID FIBRESUSPENSION BY REMOVAL OF LIQUID TO A FIBRE PULP OF AT LEAST 15% PULPCONSISTENCY AND TREATING THE SO-OBTAINED FIBRE PULP BY LEADING IT IN ASUBSTANTIALLY RADIAL DIRECTION THROUGH THE INTERSTICES OF RELATIVELY